BAƘIN RAMI DA KE HADIYE HASKENSA NA KANSA

Iyakar abubuwan da ke faruwa (event horizon) ita ce abin da ke sa baƙin rami (black hole) ya zama baƙin rami: wata iyaka da bayanta babu abin da zai iya dawowa, hatta haske. A ma’anarta, ba ta aiko mana da wata alama. Na’urar hangen nesa ta Event Horizon Telescope ta ɗauki hotunan inuwar manyan baƙaƙen ramuka a cikin taurarin galaxy M87 da Sagittarius A* — shaida ta kaikaice ta wata iyaka. Amma iyakar baƙin rami da aka haifa daga tauraro faɗinta kilomita goma-goma ne kawai, ya yi ƙanƙanta sosai don a ɗauki hotonta.

Hujjar abokin tafiya mai rauni

Masana taurari suna da wata alama. A cikin nau’i-nau’i inda mataccen tauraro yake jan iskar gas daga abokinsa, tsarin baƙaƙen ramuka masu shiru yawanci sun fi rauni kusan sau ɗari fiye da tsarin taurarin neutron masu kewaye iri ɗaya. Bayani: iskar gas da ke faɗowa tana bugun saman tauraron neutron kuma tana haskakawa, yayin da baƙin rami yake hadiye makamashin.

Raunin hujjar wani zato ne. Hujjar tana ɗauka cewa kewaye iri ɗaya na nufin saurin ciyarwa iri ɗaya. Ga kewayen da suka fi mintuna 80, abokin na iya zama brown dwarf, tauraro na yau da kullum ko kato, kuma abubuwa da yawa na iya tura kwararar iskar gas. Ainihin saurin ciyarwa ba a sani ba.

Nau’i-nau’i da ke kewayawa cikin mintuna

Qian-Qi Ma da Wei-Min Gu da Mouyuan Sun na Jami’ar Xiamen, tare da Shan-Shan Weng na Jami’ar Malamai ta Nanjing, sun juya zuwa tagwayen X-ray masu matuƙar matsewa (ultra-compact X-ray binaries). Idan kewayawar ta ɗauki ƙasa da mintuna 40, jikunan biyu suna kusa sosai har abokin zai iya zama farin dwarf kawai. Kuma kewayawar tana raguwa galibi ta hanyar fitar da raƙuman nauyi (gravitational waves).

Wannan ya sa waɗannan tsare-tsare su zama ɗakunan gwaji masu tsabta. Saurin ciyarwa a lokacin ya dogara ne kawai ga ka’idar nauyi da kuma yadda girman farin dwarf yake da alaƙa da nauyinsa. Ana iya lissafa shi daga lokacin kewayawa kaɗai, tare da wasu nauyoyin da aka ɗauka: Rana 1.4 zuwa 2 ga tauraron neutron, 3 zuwa 20 ga baƙin rami.

Ƙungiyar ta riƙe irin waɗannan tsare-tsare guda biyar, duk a cikin gungun taurari masu zagaye (globular clusters), ƙwallaye masu cunkoso na tsoffin taurari waɗanda aka san nisansu cikin 2%:

huɗu suna ɗauke da tauraron neutron, wanda aka gane ta fashewar X-ray na nukiliya mai zafi;
ɗaya, 47 Tuc X-9, yana ɗauke da baƙin rami, wanda aka gane daga yadda fitar rediyo da X-ray ɗinsa ke canzawa tare. Kewayawarsa tana ɗaukar kusan mintuna 28.

Sannan suka kwatanta matsakaicin fitar X-ray na kowane tsari, wanda aka ɗauka daga Chandra, Swift da wasu cibiyoyin lura, da saurin ciyarwarsa da aka lissafa.

Ya fi duhu sau dubu

Sakamakon shine ingancin fitar haske (radiative efficiency): rabon makamashin abin da ke faɗowa da ke fitowa a matsayin X-ray.

Ga dukan taurarin neutron huɗu, ya fi 5%.
Ga baƙin rami, ya gaza 0.03%.

Tazarar ta kai ninki ɗari zuwa dubu (biyu zuwa uku na girman ma’auni). Nau’i mafi ban mamaki: tsarin tauraron neutron M15 X-2 da baƙin rami 47 Tuc X-9 ana ciyar da su kusan daidai, kimanin gram 10¹⁶ a cikin daƙiƙa, duk da haka 47 Tuc X-9 ya fi rauni sau dubu. Ko da an ba da damar rashin tabbas har zuwa ninki goma a hasken wasu tushe, ƙungiyoyin biyu suna nan a ware.

Ina makamashin yake zuwa

Marubutan sun bayyana shi da abin da ke ƙasa. Tauraron neutron yana da saman mai tauri: ko da iskar gas mai zafi da ke shigowa ba ta fitar da haske sosai a hanyarta, makamashinta a ƙarshe ana ajiye shi a kan wannan saman kuma a sake fitar da shi. Baƙin rami ba shi da saman jiki. A ƙananan saurin ciyarwa, yawancin makamashin iskar gas ana ɗauke shi zuwa ciki a matsayin zafi — kuma yana ɓacewa a bayan iyakar.

Ga marubutan, wannan shaida ce mai ƙarfi ta iyakar baƙin rami na tauraro, ko da yake ta kaikaice ce, kamar yadda taƙaitaccen bayaninsu ya faɗa. Ta dogara ga baƙin rami guda ɗaya. Suna yin hasashen da za a iya gwadawa: duk wani sabon tauraron neutron da aka samu a irin wannan nau’i mai matsewa ya kamata ya faɗa cikin ƙungiyar masu haske, kuma duk wani baƙin rami mai kewaye iri ɗaya ya kamata ya yi rauni kamar 47 Tuc X-9.

Darasi ga manyan baƙaƙen ramuka

Binciken yana ɗauke da gargaɗi mafi faɗi. Ga baƙaƙen ramuka, haske ma’auni ne mara kyau na yawan abin da suke ci. Baƙin rami na iya girma yayin da yake ci gaba da zama mai rauni. A cewar marubutan, binciken da ke hasashen girman manyan baƙaƙen ramuka (supermassive) daga haskensu na iya rasa wani ɓangare na wannan girma.